The need to eliminate lead-based octane enhancers in gasoline has provided incentive for development of processes to produce high octane gasolines blended with lower aliphatic alkyl ethers as octane boosters. Supplementary fuels are being vigorously developed in the petroleum refining industry. Lower molecular weight alcohols and ethers such as isopropyl alcohol (IPA), isopropyl t-butyl ether (IPTBE), and diisopropyl ether (DIPE) are in the boiling range of gasoline fuels and are known to have a high blending octane number. They are useful octane enhancers. In addition, by-product propene (propylene) from which IPA and DIPE can be made is usually available in a fuels refinery, typically as a C.sub.3 + aliphatic stream rich in propene and propane. The petrochemicals industry also produces mixtures of light olefin streams int he C.sub.2 -C.sub.7 molecular weight range and the conversion of such streams or fractions thereof to alcohols and/or ethers can also provide products useful as solvents and blending stocks for gasoline.
Adapting available refinery feedstock to produce these oxygenates simultaneously as octane enhancers can involve two different olefin hydration and etherification processes, i.e. propene hydration-etherification to give DIPE and IPA. Accordingly, a challenge is provided to explore these processes to discover how they may be integrated in a manner more beneficial to the production of high octane gasoline.
Catalytic hydration of olefins to provide alcohols and ethers is established technology for production of the IPA and DIPE and is of significant commercial importance. Representative olefin hydration processes are disclosed in U.S. Pat. Nos. 4,334,890 (Kochar); 3,912,463 (Kozlowski et al.); 4,042,633 (Woods); 4,499,313 (Okumura et al.); 4,886,918 (Sorensen et al).
Olefin hydration employing medium pore and large pore zeolite catalyst is a known synthesis method. As disclosed in U.S. Pat. No. 4,214,107 (Chang et al.), lower olefins, in particular propylene, are catalytically hydrated over a crystalline aluminosilicate zeolite catalyst having a silica to alumina ratio of at least 12 and a Constraint Index of from 1 to 12, e.g., acidic ZSM-5 type zeolite, to provide the corresponding alcohol, essentially free of ether and hydrocarbon by-product. Acid resin catalysts such as "Amberlyst 15" may also be used for hydration of light olefins.
Production of ether from secondary alcohols such as isopropanol and light olefins is known. As disclosed in U.S. Pat. No. 4,182,914 (Imaizumi), DIPE is produced from IPA and propylene in a series of operations employing a strongly acidic cation exchange resin as catalyst. Recently, processes for the direct hydration of olefins to provide alcohols and ethers using porous shape selective metallosilicate zeolite catalyst, such as zeolite Beta have been disclosed in U.S. Pat. No. 4,857,664 (Huang et al.), incorporated by reference. Prior processes for hydrating olefins have often been found to be inefficient with regard to catalyst life. Maldistribution of water and hydrocarbon reactants may cause deactivation, especially with solid metallosilicate catalysts having large pores (ie 7+ Angstroms) or medium pores (5-7 A.)
It is a main object of this invention to provide a process for production of oxygenated hydrocarbons by olefin hydration, such as alcohols and/or ethers in a more economical manner and with improved yields of ethers. It is another object of the present invention to provide an improved process for the production of isopropanol and di-isopropyl ether with increased catalyst life.